This invention relates to tools, and in particular to tools for use in tightening or removing screw-threaded fasteners such, for example, as screws, bolts, nuts or the like (hereinafter and in the claims simply called "screws" for convenience).
In addition to the use of screwdrivers or spanners by hand, it is known to use power tools for the above purpose. The use of power tools is particularly advantageous in the event that a large number of screw are to be tightened or removed since in such a case the use of hand tools can be arduous and cause discomfort to the person concerned.
However particular difficulty is experienced in the use of power tools in the case of inserting and tightening or removing screws into or out of a workpiece or fixture. This is due to the lack of control exercisable by the operator of the power tool on the retention of the tool in or around the screw head and in respect of the direction of intended insertion or removal of the screw into or out of the workpiece or fixture. Also such power tools as have been proposed are expensive and unless they are used frequently such expense is not justified.
It has already been proposed to provide means whereby the abovementioned operation can be performed with the use of a power tool in a manner not having the aforementioned disadvantages, or at least in which such disadvantages are substantially reduced. In this connection see, for example, United Kingdom Pat. No. 2 088 264 B whereof the present Applicant is the inventor and a joint proprietor.
It is an object of the present invention to provide an improved power-driven device for both driving in and extracting screws which can easily and readily be converted to either of these operational modes.